Modern electronic systems are generally powered from a voltage source that provides a specified load input voltage such as a regulated direct current (“dc”) input voltage. The load input voltage is generally provided by a dedicated power converter. An important consideration in the design of such a dedicated power converter is the power conversion efficiency to produce the specified load input voltage from an input power source such as an alternating current (“ac”) mains. Power conversion efficiency is understood to be the ratio of an output power to an input power of the power converter.
A conventional power converter can generally be characterized by a nonlinear efficiency function that relates its power conversion efficiency to one or more operating parameters such as input voltage and output current. Further operating parameters such as an operating temperature are also known to affect efficiency, generally to a lesser extent. An efficiency function can be determined from laboratory measurements on a particular power converter design.
Power converters are often designed with a plurality of paralleled power processing stages (referred to as “converter stages” of a multi-stage power converter), each of which produces an equally divided proportionate part of the total output current. The several equally divided proportionate parts of the output current produced by the plurality of converter stages are summed at a circuit node to produce the total output current from the power converter. In conventional practice, the converter stages are jointly regulated to control an output characteristic of the power converter such as an output voltage, and each of the converter stages produces its equal share of the total output current. The result is the efficiency of the power converter is substantially equal to that of the efficiencies of the converter stages, which efficiencies are all substantially equal for their equally divided proportionate part of the total output current.
What is needed in the art is a technique to take advantage of the design of a power converter formed with a plurality of converter stages to produce improved power conversion efficiency. A technique that takes advantage of the plurality converter stages to improve overall power conversion efficiency without adding substantial cost to a power converter would address an industry need in view of current market trends.